Buggy code:
public class ASM implements ActionListener , AdjustmentListener { private JFrame frame ; private File asmSourceFile = null ; private JButton btnStart ; private Scanner scanner ; private Scanner scannerComma ; private Pattern patternForLabel ; private Pattern patternForName ; private Pattern patternForComments ; private String r8r8Pattern ; private String r16dPattern ; private String r8Pattern ; private Matcher matcher ; private JCheckBox cbSaveToFile ; private String defaultDirectory ; private LinkedList < PassOne > passOneList ; private SymbolTable symbolTable ; private InstructionCounter instructionCounter ; private HashMap < Integer , Byte > memoryImage ; private Tokenizer tokenizer ; private Parser parser ; private int lineNumber ; private boolean isEmptyLine ; private int currentPC ; private String symbol ; private Instruction instruction ; private Directive directive ; private String arguments ; private String comment ; public static void main ( String [ ] args ) { } public void performPassTwo ( File sourceFile ) { } private String doMemoryFile ( ) { } private String getThisValue ( int location , byte value ) { } private String getThisChar ( int location , byte value ) { } private void doList ( PrintWriter pw ) { } public static < T extends Comparable < ? super T > > List < T > asSortedList ( Collection < T > c ) { } private void saveMemoryImage ( int pc , String memImage ) { } public void performPassOne ( File sourceFile ) { } public void displaySymbolTable ( ) { } private String setMemoryBytesForDirectives ( Integer lineNumber , Directive directive , String arguments ) { } private String setMemoryBytes ( Integer lineNumber , Instruction instruction , String arguments ) { } private boolean isInstruction ( String token ) { } private boolean isDirective ( String token ) { } private void parseLine ( int lineNumber , String sourceLine ) { } private String checkForComment ( String lineToCheck ) { } private String checkForSymbol ( String lineToCheck , Integer lineNumber ) { } private String checkForInstruction ( String lineToCheck ) { } private String checkForDirective ( String lineToCheck , int lineNumber ) { } private Integer resolveSimpleArgument ( String argument , Integer lineNumbe ) { Integer ans = 0 ; if ( argument . equals ( "$" ) ) { ans = currentPC ; } else if ( symbolTable . contains ( argument ) ) { ans = symbolTable . getValue ( argument ) ; symbolTable . referenceSymbol ( argument , lineNumber ) ; } else if ( argument . matches ( ASM . stringValuePattern ) ) { String s = argument . replace ( "'" , "" ) ; byte [ ] ba = s . getBytes ( ) ; for ( byte b : ba ) { ans = ( ans << 8 ) + ( b & 255 ) ; } } else if ( argument . matches ( ASM . hexValuePattern ) ) { ans = Integer . valueOf ( argument . replace ( "H" , "" ) , 16 ) ; } else if ( argument . matches ( ASM . octalValuePattern ) ) { ans = Integer . valueOf ( argument . substring ( 0 , ( ( argument . length ( ) ) - 1 ) ) , 8 ) ; } else if ( argument . matches ( ASM . decimalValuePattern ) ) { ans = Integer . valueOf ( argument . replace ( "D" , "" ) , 10 ) ; } else if ( argument . matches ( ASM . binaryValuePattern ) ) { ans = Integer . valueOf ( argument . replace ( "D" , "" ) , 2 ) ; } else { ans = resolveExpression ( argument , lineNumbe ) ; } if ( ans == null ) { System . out . printf ( "Null<seq2seq4repair_space>ans<seq2seq4repair_space>from<seq2seq4repair_space>argument:<seq2seq4repair_space>%s%n" , argument ) ; } <START_BUG> return ans != null ? ans % 65535 : 0 ; <END_BUG> } private Integer resolveExpression ( String arguments , Integer lineNumber ) { } private void clearElements ( ) { } private String replaceWithListingFileName ( String fileName ) { } @ Override public void adjustmentValueChanged ( AdjustmentEvent ae ) { } private JFileChooser getFileChooser ( String directory , String filterDescription , String filterExtensions ) { } @ Override public void actionPerformed ( ActionEvent ae ) { } public void appInit ( ) { } public ASM ( ) { } private void initialize ( ) { } private static HashMap < String , Directive > directives ; private static HashMap < String , Instruction > instructions ; private static final String hexValuePattern = "[0-9][0-9A-Fa-f]{0,4}H" ; private static final String octalValuePattern = "[0-7]+[O|Q]" ; private static final String binaryValuePattern = "[01]B" ; private static final String decimalValuePattern = "[0-9]{1,4}D?+" ; private static final String stringValuePattern = "\\A\'.*\'\\z" ; public static final String FILE_LOCATION = "." ; private static final String CODE = "Code" ; public static final String ASSEMBLER_SUFFIX = "asm" ; private JTextArea txtSource ; private JTextArea txtListing ; private JScrollPane scrollSource ; private JScrollPane scrollListing ; JLabel lblSource ; JLabel lblListing ; }

Fix:
return ans != null ? ans & 65535 : 0 ;